Myocardial infarction

It’s the Heart Attack Season: MI Risk Highest on Christmas Eve

'Cause just exactly at ten o'clock

the MI risk is at its peak...

Risk of myocardial infarction (MI) is higher during the Christmas/New Year holiday season, and during midsummer holidays, according to the results of a recent study.

Although current understanding of ischemic heart disease is that it is “multifactorial with predisposing modifiable and non-modifiable risk factors,” previous research has suggested that external factors could trigger the onset of MI, with some evidence showing peak risk on Christmas and New Year’s Day in the Western world.

To explore circadian rhythm aspects and the effects of national holidays and major sporting events as triggers of MI, researchers conducted a retrospective observational study using data from a nationwide coronary care unit registry (SWEDEHEART).

Overall, 283,014 cases of MI were reported between 1998 and 2013. The researchers found that Christmas (Christmas Eve, Christmas Day, Boxing Day, New Year’s Eve, New Year’s Day, and the Epiphany) and Midsummer holidays (Midsummer Eve and Midsummer Day—also known as St John’s Day) were associated with higher risk of MI (incidence rate ratio 1.15, 1.12), with the highest risk observed on Christmas Eve (1.37) at 10pm. No increased risk was observed during Easter holidays (Good Friday, Easter Eve, Easter Day, and Easter Monday) or during sporting events (FIFA World Cup, UEFA European Championship, and Winter and Summer Olympic Games).

“In this nationwide real-world study covering 16 years of hospital admissions for myocardial infarction with symptom onset documented to the nearest minute, Christmas and Midsummer holidays were associated with a higher risk of myocardial infarction. Consistently, we observed a higher risk in older and sicker patients, suggesting a role of external triggers in vulnerable patients.”

—Michael Potts

Mohammad MA, Karlsson S, Haddad J, et al. Christmas, national holidays, sport events, and time factors as triggers of acute myocardial infarction: SWEDEHEART observational study 1998-2013 [published online December 12, 2018]. BMJ. doi: